Original developed for treatment of myocardial
ischemia (angina).Cells in the corpus cavernosum produce NO [nitrous oxide]
during sexual arousal in response to nonadrenergic, noncholinergic neurotransmission.NO stimulates the formation of cyclic GMP, which leads to relaxation of smooth muscle of the corpus cavernosum and
penil arteries, engorgement of the corpus cavernosum, and erection…. Not surprisingly, PDE5 inhibitors have assumed
the status of widely used recreational drugs.Tadalafil (Cialis) and vardenafil (Levitra) share similar therapeutic
efficacy and side-effect profiles with sidenafil (Viagra).[Cialis lasts the
longest].—Goodman & Gilman, 11th Ed. 2006, p829

“Most tadalafil clinical trials excluded patients with unsuccessful
prior treatmentwith sildenafil citrate (sildenafil).”J Sex Med, 2006 Jul;3(4);668-75.ANOTHER WAY TO MANUFACTURE
POSITIVE RESULTS.Moreover most of the studies are funded by the drug manufactures,
thus the testing and reporting of results are slanted.Of the six studies below,
only one seem to maintain a critical prospective.--JK

With sever ED (subtracting placebo
effect), only 23% and 40% were satisfied for two questions (below).For most
with sever ED the improvement is none or marginal.

The efficacy
of sildenafil citrate (Viagra) in clinical populations: an update.

Carson CC., Burnett AL, et al

{a meta study} Efficacy evaluations included the International Index of Erectile Function, a global efficacy
question ("Did treatment improve your erections?"), and a patient-recorded event log of sexual activity. Significantly improved
erectile function was demonstrated for sildenafil compared with placebo for all efficacy parameters analyzed (P <0.02 to
0.0001), regardless of patient age, race, body mass index, ED etiology, ED severity, ED duration, or the presence of various
comorbidities. Long-term effectiveness was assessed in 3 open-label extension studies.Of those who continued long-term therapy (1 to 3 years) with sildenafil, >95% of patients reported that they were
satisfied with the effect of treatment on their erections, and that treatment had improved their ability to engage in sexual
activity

Correlation of improved
erectile function and rate of successful intercourse with improved emotional well-being assessed with the Self-Esteem And
Relationship questionnaire in men treated with sildenafil for erectile dysfunction and stratified by age.The psychosocial measures of well-being
assessed with the SEAR were positively correlated (range 0.60-0.86, P < 0.0001) with erectile function, the frequency of
achieving erections that allowed satisfactory sexual intercourse, the percentage of successful sexual intercourse attempts,
and global treatment efficacy.

Pooled data from 6549
men with ED provided strong proof and improved characterization of the response to sildenafil. Almost half of men with ED
and a baseline IIEF EF domain score classified as "severe ED" (< or = 10) shifted to a score classified as "no ED" (>
or = 26). Sildenafil recipients showed greater mean improvement from baseline to end point in IIEF Q2 scores versus placebo,
regardless of baseline ED severity, and a higher mean percentage of successful sexual intercourse attempts occurred during
the last 4 weeks of treatment versus placebo (5.4-fold vs 2.0-fold increase from baseline). At end point, 95% of men who scored
"no ED" on the IIEF EF domain and 92% of men who reported "almost always/always" achieving an erection hard enough for penetration
(IIEF Q2) had graded their erections hard (rigid) enough for penetration (grade 3) or completely hard and fully rigid (grade
4) during the last 4 weeks of treatment,

With sever ED (subtracting placebo
effect), only 23% and 40% were satisfied for two questions (below).For most
with sever ED the improvement is none or marginal.

RESULTS: Of the 443 men
who entered the trial, 409 (mean age, 52 years) formed the intent-to-treat population. Mean baseline demographics and ED severity
measures were balanced between treatment groups except for a higher percentage of patients naive to sildenafil in the tadalafil
group compared to placebo (50% versus 36%). EDITS score of 84
(95%CI 80, 86), which was significantly higher than the median score for placebo-treated patients of 41 (95%CI 32, 59; p <
0.001; Wilcoxon test). The proportion of patients satisfied with treatment (defined as final EDITS score greater than 50)
was 87% for the tadalafil-treated group and 46% for the placebo-treated group (p < 0.001; exact test).

Some scare misinformation
has been circulating about Viagra and adverse visual effects including blindness. One sources is www.worstpills.org. I have failed to substantiate this in an
internet search.“The drug also mildly inhibits PDE6, which controls the
levels of cyclic GMP in the retina.Visually, this can result in seeing a bluish
haze or experiencing light sensitivity.Although no retinal damage has been reported,
no long-term studies have been reported—Goodman & Gilman, 11 ED. 2006, p. 1728.